Mask



FIG. 1 is a front, left-side, top perspective view of a mask, showing the new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left-side elevational view thereof;

FIG. 5 is a right-side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines depict parts of the mask that form no part of the claimed design. 

CLAIM The ornamental design for a mask, as shown and described. 